Photolithographic patterning and etch is a common technique by which integrated circuit components are fabricated on a substrate. A desired pattern is created in a masking material, such as photoresist, over an underlying substrate material to be etched. The patterned masking material thereby has a series of spaced projections atop underlying material. The underlying material is then etched typically using a chemistry that is selective to etch the material underlying the masking material at a greater rate than the masking material itself, thereby transferring the pattern of the masking material/projections into the substrate material therebeneath. Typically, the masking material is then etched away in a manner that is selective to remove it relative to the underlying substrate material in which the pattern was formed.
Ideally, it is desired that the sidewalls of the projections of the masking material be substantially vertical and very smooth. Unfortunately, and especially as device dimensions and, accordingly, mask features get smaller, the sidewalls of the masking projections can become intolerably rough. Further, masking features can have varied roughness at different locations on the sidewalls or different roughness in one projecting masking feature relative to another projecting masking feature. Accordingly, a subsequent etch of the material underlying the mask can produce less than desired results.
One prior art manner of smoothing rough sidewalls of a photoresist masking feature comprises a short isotropic etch using a halogen-containing gas after mask formation. However, such does not significantly improve sidewall roughness, reduces the thickness of the photoresist masking blocks, and in certain instances can form breaks in long-running masking features, such as in parallel lines.
While the invention was motivated in addressing the above identified issues, it is in no way so limited. The invention is only limited by the accompanying claims as literally worded, without interpretative or other limiting reference to the specification, and in accordance with the doctrine of equivalents.